D. Blankevoort & Zn BV

There is one known measurement from this shipyard, of a sand dredger from 1970 (Piet Hein). It was common for "wet" contractors at that time to build their equipment themselves, or to have it built under their own supervision. This dredger was build in Lisse, at this time, there was a company in Lisse (G.A. Koning) that was a shipyard specializing in dredging equipment. Perhaps it was built there? The shipyard built mainly dredging equipment, pontoons and/or work vessels.
There is only 1 known registrated new build for this shipyard.